1. Field of the Invention
This invention relates to solids handling, and more particularly to apparatus and methods for introducing particulate solids into the bottom of a solids upflow vessel, such as a vertical solids upflow retort used for heat treating oil-producing or oil-containing solids to recover oil and/or gas therefrom.
2. Description of the Prior Art
The problem of transporting particulate solids from a solids feed supply, such as a bin or reservoir of the particulate solids, into the bottom of a solids upflow vessel has been encountered in diverse operations, exemplary of which are the feeding of oil-producing and/or gas-producing solids, such as oil shale, tar sand, bituminous coal, oil-saturated diatomaceous earth, and the like into the bottom of a vertical solids upflow retort for treating the solids to recover oil and/or gas therefrom, and the production of synthesis gas by the reaction of gas containing steam with carbonaceous solids such as coal, coke, and the like.
In these operations, difficulties are encountered in the design and operation of mechanical feed systems because of the nature of the particulate solids being transported, typical solids being abrasive and difficult to handle on the one hand and on the other being friable and tending to abrade, thereby forming large quantities of undesirable fine particles. Feeder devices used to introduce solids into the bottom of an upflow solids bed must move the solids against the weight of the solids bed. Also, it is often the case that the solids must be transported from a storage bin at atmospheric pressure into a solids upflow vessel which operates at a superatmospheric pressure. These factors, coupled with the often gigantic size of the equipment required to obtain the desired solids feed capacity, and the fact that in some applications the feeder device must operate at elevated temperatures and in contact with liquids and/or gases produced in the solids treating process, produce difficult design problems involving large and complex mechanical forces and complicated mechanical loadings that must be adequately provided for in the feeder design.
A number of different apparatus and methods for introducing particulate solids into the bottom of a solids upflow vessel have been proposed. U.S. Pat. Nos. 2,501,153 to Berg, 2,640,014 to Berg, 2,875,137 to Lieffers et al. and 2,895,884 to Switzer disclose solids feeding apparatus and methods in which particulate oil shale is introduced upwardly into the bottom of a vertical retort by means of a piston reciprocating in a feed cylinder that is oscillated between an outlet of a shale feed reservoir and the bottom solids inlet of the retort. While such oscillating feeder apparatus can be satisfactorily employed to introduce particulate solids into a solids upflow vessel, a number of problems and limitations are encountered when using such feeders in large capacity commercial units, such as oil shale retorts having capacities on the order of 10,000 tons of oil shale per day or more. Specifically, oscillating feeder apparatus having these capacities are extremely large and require substantial clearance between the supporting foundation and the bottom of the retort, increasing the height and cost of the retort structure. The clearance between the arcuate seal plates oscillated with the feed cylinder, and the bottoms of the feed reservoir and retort must be extremely small, such as about 0.030 inch or less. Machining of these parts to such close tolerances is very difficult and at best is very costly.
U.S. Pat. No. 4,033,467 to Bewley et al. and 4,037,736 to Pownall et al. disclose solids feeding apparatus and methods in which particulate solids are introduced upwardly into the bottom of a vertical solids upflow vessel by means of twin pistons reciprocating in twin feed cylinders that are rotated and reciprocated, respectively, between one or more solids feed chutes and the bottom solids inlet of the solids upflow vessel. While such feeders can be satisfactorily employed to introduce particulate solids into a solids upflow vessel at very high rates, the mechanical complexity and enormous size of these feeders results in a very high cost of construction and relatively high operating expense.
U.S. Pat. No. 2,871,170 to Bewley et al. discloses a solids feeding apparatus and method in which particulate solids are introduced upwardly into the bottom of a vertical solids upflow vessel by means of a piston reciprocating in a stationary feed cylinder that is axially aligned with the bottom solids inlet of the solids upflow vessel. Twin horizontally reciprocatable scoops forceably introduce additional solids into the feed cylinder while slide plates prevent backflow of solids from the retort. The volume of solids introduced into the feed cylinder by the scoops must necessarily be carefully controlled in this apparatus to avoid overfilling the feed cylinder and therefore a relatively elaborate solids flow control device is provided to regulate the solids introduction rate. While this apparatus has the advantage of having stationary hydraulic actuating cylinders, the necessity of having the solids flow control device on the feed chute is undesirable from a practical standpoint in a large scale commercial plant. Accordingly a need exists for a mechanically simple and effective apparatus and method for introducing particulate solids upwardly into a solids upflow vessel at high rates.
Accordingly, a primary object of this invention is to provide an improved apparatus and method for introducing particulate solids upwardly into the bottom of a solids upflow vessel.
Another object of this invention is to provide a mechanically simple and effective solids feeding apparatus and method having lower construction and operating costs than the prior art apparatus and methods.
Yet another object of this invention is to provide a solids feeding apparatus in which the hydraulic cylinders and hydraulic lines are stationary and the number of moving parts is minimized so as to reduce the amount of maintenance required.
A further object of this invention is to provide a solids feeding apparatus in which the moving parts thereof are relatively easily accessible for maintenance and repair.
A still further object of this invention is to provide a solids feeding apparatus and method in which the forces applied to the particulate solids being fed are reduced to a practical minimum.
Additional objects, advantages and features of the invention will become apparent to those skilled in the art from the following description when taken in conjunction with the accompanying drawings.